It has been estimated that between 2% and 5% of clean surgeries result in surgical site infections (SSI). Patients who develop SSI can be 60% more likely to spend time in an ICU, can be 5 times as likely to be readmitted, can have a mortality rate twice that of noninfected patients, can have an average of 7 days additional length of hospital stay, and can have an average of about $3,000 additional costs. It has been estimated that about 40-60% of SSIs can be preventable (see, e.g., Barie P S, Eachempati S R. Surgical site infections. Surg Clin North Am 2005; 85(6):1115-35, viii-ix).
It has been approximately 50 years since Deryl Hart and colleagues at Duke University showed that ultraviolet (UV) irradiation of surgical wounds can be a highly effective methodology for reducing surgical wound infection rates (see, e.g., Hart D. Bactericidal ultraviolet radiation in the operating room. Twenty-nine-year study for control of infections. J Am Med Assoc 1960; 172:1019-28). However, UV radiation can be a hazard both to the patient and to the operating team, and the use of additional clothing, hoods, and eye shields for protection can be both cumbersome and costly, preventing widespread use of the technique.
UV radiation can be a very efficient bactericidal agent, and the mechanisms by which it mutates and kills bacteria, as well as human cells, are well established (see, e.g., Mitchell D L, Nairn R S. The biology of the (6-4) photoproduct. Photochem Photobiol 1989; 49(6):805-19; Witkin E M. Ultraviolet mutagenesis and inducible DNA repair in Escherichia coli. Bacteriol Rev 1976; 40(4):869-907; Koch-Pain C A, Amundson S A, Bittner M L, Meltzer P S, Fornace A J, Jr. Functional genomics of UV radiation responses in human cells. Mutat. Res. 2004; 549(1-2):65-78; and Harm W. Biological effects of ultraviolet radiation. Cambridge, UK: Cambridge University Press, 1980). Ultraviolet germicidal irradiation (UVGI) has been used to break down microorganisms in food, air, and water purification, UVGI typically uses a short wavelength of UV, typically in the UVB or UVC range, to destroy nucleic acids in small organisms, removing their reproductive capabilities. UV irradiation (including UVGI) is typically produced with low-pressure mercury lamps, which can produce a range of UV wavelengths, ranging from UVA (wavelengths 400 to 320 nm) to UVB (wavelengths 320 to 290 nm) to UVC (wavelengths 290 to 100 nm). FIG. 1 shows the spectrum of UV wavelengths emitted from a typical mercury UV lamp. UVGI is typically produced by mercury-vapor lamps that emit at around 254 nm. However, UVGI lamps may be harmful to humans and other life forms, and are typically shielded or in environments where exposure is limited.
UV lamps can also facilitate a UV emission from an excited molecule complex (e.g., an exciplex, such as either krypton-bromine or krypton-chlorine), using arrangements called excilamps. The basic theory behind exciplex UV emission was developed in the 1970s (see, e.g., Lorents D C. A model of rare-gas excimer formation and decay and its application to vuv lasers. Radiat. Res. 1974; 59(2):438-40; and Measures R M Prospects for developing a laser based on electrochemiluminescence. Appl Opt 1974; 13(5):1121-33). The first excimer lasers were made in the 1980s and they are now in common use, for example, e.g., in LASIK opthalmic surgery (see, e.g., Pallikaris I G, Papatzanaki M E, Stathi E Z, Frenschock O, Georgiadis A. Laser in situ keratomileusis. Lasers Surg Med 1990; 10(5):463-8). Current excimer lasers, however, are typically not feasible for wound sterilization both in terms of beam size (e.g., excimer laser beams are very narrow) and their high cost. In the past, an excimer lamp (excilamp) has been developed in Russia (see, e.g., Sosnin E A, Oppenlander T, Tarasenko V F. Applications of capacitive and barrier discharge excilamps in photoscience. J. Photochem. Photobiol C: Photochem. Rev. 2006; 7:145-63), which can produce a wide high-intensity beam of single-wavelength UV radiation. These lamps can be small, inexpensive (e.g., ˜$1,000), high powered (e.g., wound irradiation time can be a few seconds), and long-lived (e.g., 1,000 to 10,000 hours). Certain papers (see, e.g., Sosnin E A, Avdeev S M, Kuznetzova E A, Lavrent'eva L V. A bacterial barrier-discharge KrBr Excilamp. Instr. Experiment. Tech. 2005; 48:663-66; Matafonova G G, Batoev V B, Astakhova S A, Gomez M, Christofi N. Efficiency of KrCl excilamp (222 nm) for inactivation of bacteria in suspension. Lett Appl Microbiol 2008; 47(6):508-13; and Wang D, Oppenlander T, El-Din M G, Bolton J R. Comparison of the disinfection effects of vacuum-UV (VUV) and UV light on Bacillus subtilis spores in aqueous suspensions at 172, 222 and 254 nm. Photochem Photobiol 2010; 86(1):176-81) have been published on their bactericidal properties (as expected they are highly efficient), but the concept that these lamps will kill bacteria but not human cells is not described.
Thus, there may be a need to address at least some of the deficiencies and/or issues that to date remained with respect to the above-described conventional systems and methods.